0 <= i, j < words.length,

i != j, and

words[i] + words[j] (the concatenation of the two strings) is a .

Return an array of all the palindrome pairs of words.

Example 1:

Input: words = ["abcd","dcba","lls","s","sssll"]
Output: [[0,1],[1,0],[3,2],[2,4]]
Explanation: The palindromes are ["abcddcba","dcbaabcd","slls","llssssll"]

Example 2:

Input: words = ["bat","tab","cat"]
Output: [[0,1],[1,0]]
Explanation: The palindromes are ["battab","tabbat"]

Example 3:

Input: words = ["a",""]
Output: [[0,1],[1,0]]
Explanation: The palindromes are ["a","a"]

Constraints:

1 <= words.length <= 5000
0 <= words[i].length <= 300
words[i] consists of lowercase English letters.

23:T437,You are given a **0-indexed** array of **unique** strings `words`. A **palindrome pair** is a pair of integers `(i, j)` such that: * `0 <= i, j < words.length`, * `i != j`, and * `words[i] + words[j]` (the concatenation of the two strings) is a palindrome. Return _an array of all the **palindrome pairs** of _`words`. You must write an algorithm with `O(sum of words[i].length)` runtime complexity. **Example 1:** **Input:** words = ["abcd","dcba","lls","s","sssll"] *

Palindrome Pairs

Problem Description

Problem Description

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